Method for forming a concealed image by sublimination

ABSTRACT

A teaching process which makes use of a copy sheet having a visible image, a master sheet having a visible image keyed to the visible image on the copy sheet and a coating associated with the imaged master containing an invisible heat volatilizable material capable of reaction with a developer component for development of color which includes positioning the copy sheet with its printed side in surface contact with the coating and radiating the master sheet to develop a corresponding heat pattern to cause volatilization of the material in the corresponding areas of the coating for transfer to provide a latent image on the corresponding areas of the copy sheet, and in which the latent image is developed by wetting with the development material.

United States Patent [72] Inventor Richard E. Thomas Chicago, Ill. [211App]. No. 768,372 [22] Filed Oct. 17, 1968 [45] Patented Nov. 2, 1971[73] Assignee A. B. Dick Company Niles, Ill. The portion of the term ofthe patent subsequent to June 24, 1986, has been disclaimed.

[54] METHOD FOR FORMING A CONCEALED IMAGE BY SUBLIMINATION 4 Claims, 6Drawing Figs. [52] U.S.Cl l17/l.7, 35/9 R, 101/469, 101/470, 101/471,ll7/36.7, 117/37 R, 250/65 T [51] Int. Cl 841m 5/12 [50] Field of Search117/1.7, 36.2, 36.7, 37; 35/9; 101/469, 470, 426, 426 CR; 250/65 T [56]References Cited UNITED STATES PATENTS 2,993,805 7/1961 Kay 117/623,210,544 10/1965 Marx et al 250/65 3,262,386 7/1966 Gordon 101/149.4

Prater; M. P., Superthreshold Impact Heating Printing" IBM TechnicalDisclosure Bulletin vol. 1 No. 6, pg. 4 April 1959 PrimaryExaminer-William D. Martin Assistant Examiner- Edward J. CabicAnorney-McDougall, Hersh, Scott & Ladd ABSTRACT: A teaching processwhich makes use of a copy sheet having a visible image, a master sheethaving a visible image keyed to the visible image on the copy sheet anda coating associated with the imaged master containing an invisible heatvolatilizable material capable of reaction with a developer componentfor development of color which includes positioning the copy sheet withits printed side in surface contact with the coating and radiating themaster sheet to develop a corresponding heat pattern to causevolatilization of the material in the corresponding areas of the coatingfor transfer to provide a latent image on the corresponding areas of thecopy sheet, and in which the latent image is developed by wetting withthe development material.

This invention relates to a sheet having a visible image in the form ofan examination Ysheet, instructional material, or teaching device, andan invisible or latent image keyed to the visible image for developmentof the invisible or latent image by a special developmentmaterial in theform of a liquid, pencil, crayon and the like containing one or morecomponents for reaction with the invisible material present in thelatent image for visual development thereof.

Concealed images keyed to visual instructional material of the typedescribed have found considerable,acceptance in-the field ofexamination, self-instructional, material, and other devices used in theeducational field. Reference may be made to the copending applicationSer. No. 574,743, filed-Aug. 24,

" 1966, now U .S. Pat. No. 3,451,143, and entitled Spirit Duplicationwith Visible and Concealed Images" for a fuller description of onetechnique for preparation of copy of the type described by a spiritduplicating processarid for the application and use of the same.

it is an object of thisjnvention to produceand to provide a method forproducing copy of the type described containing the combination ofvisible images and invisible or concealed images keyed to the visibleimage and to a new and novel means and elements for use in thepreparationof same.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawing in which:

FIG. 1 is a perspective view partially in section of an imaged originalembodying the feature of this invention;

FIG. 2 is a perspective elevational view partially in section of theoriginal in position for imaging a copy sheet;

FIG. 3 is a perspective view partially in section of the imaged copysheet;

H6. 4 is a perspective view partially in section of the copy sheet shownin FIG. 3 with the portion selected by the user being marked;

FIG. 5 is a perspective view partially in section similar to that ofFIGS. 3 and 4 with the concealed image developed; and

F IG. 6 is a perspective view partially in section of a transfer sheetwhich may be used in the practice of this invention.

In accordance with the concept of this invention, the.invisible orconcealed image is transferred as a latent image keyed to the visibleimage on a copy sheet by the process of sublimation or volatilization ofan invisible image forming material directly from acoated master to theprinted copy sheet to form the latent invisible image thereon. Thisenables a number of unique ramifications from the standpointofflexibility in use as well as in application. For purposes ofillustration, the invention will be described with reference to itspractice in examinations, it being understood that the various and manyother uses will be immediately apparent from thedescription hereof andfrom the description of the aforementioned copending application. i

It has been found that there are a number of materials which are capableof transfer from one surface to another and which are invisible in theirstate of transfer until developed by reaction with another component forcolor formation. The above defines the essential characteristics of thematerial required to be present in the transfer coating to form theinvisible conccaled image on the copy sheet: namely, a colorless orinvisible compound or component, volatility of the compound atrelatively low temperature of the order of less than l,000 F. andpreferably less than 500 F. but above 150 F., and capable of colordevelopment upon reaction of the compound with another component.Representative are such materials as salicylic acid, vanillin, benzoicacid and antipyrine. Such materials are capable of being volatilized inresponse to a heat pattern generated upon infrared radiation of anoriginal containing an infrared ray absorbing-heat generating image onone or the other side of the coated master sheet. Each of the materialsdescribed as capable of use informing the latent concealed image canimmediately be, developed by reaction with ferric chloride, for example.

Theinvisible material usedin the formation of the latent concealed imagecan be embodied as a coating onthe imaged master or on a separatetransfer sheet adapted to be used with the imaged master.

The ferric chloride or-other. development component can be embodied inthe developing material, preferably in solution in a fluid with whichthe entire copy sheet, can-.be wet for image development or as acomponent of an ink, pencil .or other marking material.

Having described-the basic concepts of the invention, illustration willnow be made by way of-the following example:

FIG. 1 illustrates a master sheet l0-having a box 12 in the form of anoriginal image of infrared ray absorbing material. The backside of thesheet is provided with a coating 14 of salicylic acid,.or vanillin, orbenzoicacid, or antipyrine. applied by rollercoating, spraycoating .orthe like coating technique from a dilute solution correspondingzto aboutl-l0 perccnt by weight of the invisible latent image forming material.

Instead of supplying the overall layer j 14, containing the latentimaging material, on the backside of the-imaged master a 10, it may beembodied within or ona thin absorbent transfer sheet 14''.

The copy sheet 20 is provided with the information or examinationquestions '22 in the form'of avisible image with a number of boxes 24keyed to the. question for selection of one as the answer to be'given bythe pupil for'the particular question.

The box which represents'theproper answer is provided .with theinvisible, concealed imaging material by positioning the copy sheet 20.with the imaged side in surface contact with the transfer coating 14 or14', and the master is radiated with radiations 30 rich in infraredwhereby the radiations are absorbed by the imaged portion of the masterto generate a heat pattern sufficient to cause vaporization of latentimaging material in the area corresponding to the heat pattern fortransfer to the appropriate box 26 on the copy sheet. Thus, the boxwhich represents the correct answer is provided with the latent imagingmaterial but its presence is not observed by the pupil taking theexamination.

The pupil selects one of the boxes as his answer and marks the box witha conventional pencil, ink or marking material to inscribe a visiblemark 28 in the box selected for the answer.

For grading and/or for permanent record which can be returned to thepupil, the copy sheet is wet overall with a developing liquid, such as adilute aqueous solution of ferric chloride (0.1-2 percent by weight).This will react with the latent imaging material in the box 26 forvisual development ofthe box representing'the correct answer. lf itcoincides with the answer marked by the student, this will immediatelybe made visible for use by the teacher in grading and as a permanentrecord for the student. If the student has marked another box, this willalso immediately be made visible for grading andrecord purposes.

instead of development by the teacher with a developing solution, theinstrument with which the sheet is marked by the student can be bothcolored and contain the ferric chloride or other developing materialimmediately to indicate to the student when he has selected the correctanswer and to indicate to the teacher when the student has firstselected the desired answer or an answer other than the correct answer.

It will be understood that instead of effecting volatilization fortransfer of invisible imaging material from the transfer coating to thecopy sheet by way of infrared radiation of an original, heat patternskeyed to the copy sheet and otherwise generated as by means of a dieplate or template may be used to effect volatilization for transfer ofthe concealed imaging material to the copy sheet.

It will be understood that other changes may be made in the details ofconstruction, arrangement and operation without departing from thespirit of the invention, especially as defined in the following claims.

1. in a copy making process in which use is made of a copy sheetcontaining a visible image on one surface thereof and a latent invisibleimage containing a material capable of visual development with adeveloping material and subsequently developing the latent invisibleimage with a developing material, the steps of positioning the surfaceof the copy sheet having the visible image thereon in surface contactwith a layer on one side of a master sheet containing an invisiblematerial which is heat volatilizable at a temperature above 150 F. andwhich is capable of reaction with the developing material for thedevelopment of a visual image, said master sheet containing a radiationabsorbing heat-generating visible image keyed to the visible image onthe copy sheet, radiating the master sheet with radiations which areabsorbed by the visible image thereon to develop a corresponding heatpattern in the master sheet which transfers to the layer to causevolatilization of said material in the corresponding areas of the layerfor transfer to provide a latent concealed image in the correspondingareas of the copy sheet.

2. The process as claimed in claim 1 in which the layer is a transfercoating on the backside of the imaged master.

3. The process as claimed in claim 1 in which the transfer coating ispresent in a sheet separate and apart from the master and in which thetransfer sheet and master are positioned together on the copy sheet fortransfer of the invisible image with the transfer sheet between theimaged surface of the copy sheet and the imaged master.

4. In a copy making process in which use is made of a copy sheetcontaining a visible image on one surface thereof and a latent invisibleimage containing a material capable of visual development with adeveloping material and subsequently developing the latent image withthe developing material, the steps of positioning the surface of thecopy sheet having the visible image in surface contact with a layer onone side of a master sheet containing an invisible material which isheat volatilizable at a temperature above F. and which is capable ofreaction with the developing material for the development of a visualimage, applying a heat pattern defining the invisible image to thesurface of the master sheet keyed to the copy sheet which causesvolatilization of said material from the corresponding areas of thelayer for transfer from the master sheet to the copy sheet to provide alatent concealed image in the corresponding areas of the copy sheet.

t I t i i

2. The process as claimed in claim 1 in which the layer is a transfercoating on the backside of the imaged master.
 3. The process as claimedin claim 1 in which the transfer coating is present in a sheet separateand apart from the master and in which the transfer sheet and master arepositioned together on the copy sheet for transfer of the invisibleimage with the transfer sheet between the imaged surface of the copysheet and the imaged master.
 4. In a copy making process in which use ismade of a copy sheet containing a visible image on one surface thereofand a latent invisible image containing a material capable of visualdevelopment with a developing material and subsequently developing thelatent image with the developing material, the steps of positioning thEsurface of the copy sheet having the visible image in surface contactwith a layer on one side of a master sheet containing an invisiblematerial which is heat volatilizable at a temperature above 150* F. andwhich is capable of reaction with the developing material for thedevelopment of a visual image, applying a heat pattern defining theinvisible image to the surface of the master sheet keyed to the copysheet which causes volatilization of said material from thecorresponding areas of the layer for transfer from the master sheet tothe copy sheet to provide a latent concealed image in the correspondingareas of the copy sheet.